Lubricating oil for an internal combustion engine commonly contains additives to reduce and/or control deposits, wear, and/or corrosion. Similarly, liquid hydrocarbon fuels for an internal composition engine also commonly contain additives to control and/or reduce the formation of deposits. A polyolefin is useful as an additive in a fuel or lubricant as a viscosity modifier. To be useful as a viscosity modifier at both low and high temperatures, such a polymer must have a sufficient thickening effect on a light lubricating oil at high temperatures and a limited thickening effect on the light lubricating oil at low temperatures.